Rollover speed

[Loren]

I've pulled average .998 G's (two laps each direction, 200' asphalt skidpad). That's on a custom tuned coilover suspension (K-Sport + custom rear springs + TRD swaybar + alignment) and really grippy street tires (195/55-15 Dunlop Direzza Sport Z1 Star Spec). If I put a set of competition tires (slicks) on the car, I could easily do 1.1 G's or more.

But, that's really no answer to your question. Castrex gave a more correct answer.

If you go out and do something stupid, you can get any car to go over... especially one with a soft suspension.

The single most important factor in the equation is the driver. Your Yaris ain't gonna roll itself... nor is it going to get around a corner really fast a pull a lot of G's by itself.

In a steady-state turn (like a skidpad with a smooth driver), a stock Yaris is going to understeer before it rolls over. The front tires will simply give up at a certain speed and you'll start pushing outward in the turn. The only way to get the car to roll over is to introduce another variable that will trip up the car. Something like a hole or a curb or big chunk of something in the road... or simply a dumb driver input, like yanking the wheel in the opposite direction and then back again.